A touch screen is used in various portable electronic devices such as a personal digital assistant (PDA), a tabletop and a mobile device. The touch screen can be operated by a pointing device (or a stylus) or a finger.
However, since an input device of a device including the touch screen generally has a fixed shape and size, it is very difficult or impossible to customize the input device of the device for the purpose of user's convenience. Moreover, the device including the touch screen tends to have wider and bigger touch screen, and thus, a user has a difficulty in operating the device by one hand throughout the touch screen.
Also, regarding a touch technology used in a touch panel, the user is allowed to operate user interface by necessarily touching the screen. Here, the screen of the panel may be damaged with the increase of the number of the touches. Therefore, there is a need to improve the user's convenience by providing an intuitive interfacing technology of providing a natural interface and of enhancing the interaction between humans and computers.